Begin by preheating your oven to 350°F (180°C) on a regular bake setting, ensuring the oven rack is positioned in the center. Prepare two 6-inch baking pans by greasing or spraying them and lining the bottoms with parchment paper.

In a large mixing bowl, use an electric mixer or a stand mixer fitted with a whisk attachment to combine the eggs and sugar at medium speed until well mixed.

While the mixer is still running at medium speed, gradually add the melted butter, vegetable oil, sour cream, and lemon zest, whisking until everything is incorporated.

In a separate medium bowl, mix together the flour, baking powder, and salt. Slowly add this dry mixture to the egg mixture while the mixer is set to low to prevent flour from flying out. Once combined, increase the speed to medium and mix briefly until the batter is smooth.

Evenly divide the batter between the two prepared cake pans, smoothing the tops with a spatula. Bake in the preheated oven for 25-35 minutes, or until a skewer inserted into the center comes out clean. Baking times may vary based on your oven and the type of pans used.

Once baked, remove the cakes from the oven and let them cool in the pans on a cooling rack for 20 minutes.

While the cakes are cooling, prepare the lemon syrup. In a medium saucepan, combine the sugar and water over medium heat, stirring until the sugar dissolves. Then, add the lemon juice and heat until the mixture is just about to boil. Remove from heat and allow to cool until warm.

After the cakes have cooled for 20 minutes, use a cocktail stick or fine skewer to poke numerous holes in the surface of each cake, pressing in about an inch deep.

Pour the warm lemon syrup evenly over the cakes, allowing them to soak in the syrup. Let the cakes sit in the pans with the syrup for 3-4 hours before removing them.

If you're not serving the cake immediately, you can wrap the layers tightly in plastic wrap and refrigerate them for up to 24 hours.

To assemble the cake, whip the heavy cream with the sugar in a bowl until soft peaks form. Place one layer of the cake on a serving plate and spread a layer of whipped cream on top. Carefully place the second layer on top.

Dust the top of the cake with icing sugar before serving. For a decorative touch, you can use a cake stencil or a paper doily.

When slicing the cake, insert the knife vertically into the center and cut downwards towards the outside to minimize the whipped cream from spilling out.

If you made a single layer or loaf cake, simply slice and serve with a dollop of whipped cream on top or on the side. Store any leftovers in an airtight container in the fridge for up to three days.